Method of removing solids by modifying a liquid level in a distillation tower

ABSTRACT

The present disclosure provides a method of separating a feed stream in a distillation tower. The method includes maintaining a controlled freeze zone section in a distillation tower; maintaining a melt tray assembly within the controlled freeze zone section that operates at a temperature and pressure at which solid melts; forming solids in a controlled freeze zone section; raising a liquid level of a liquid in the melt tray assembly when the solids accumulate on a mechanical component in the controlled freeze zone section; raising a liquid temperature of the liquid while raising the liquid level; and lowering the liquid level after at least one of (a) a predetermined time period has passed and (b) an alternative temperature of the mechanical component is within an expected temperature range of a baseline temperature of the mechanical component.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the priority benefit of both U.S. Provisionalpatent application No. 61/912,983 filed Dec. 6, 2013 entitled METHOD OFREMOVING SOLIDS BY MODIFYING A LIQUID LEVEL IN A DISTILLATION TOWER, theentirety of which is incorporated by reference herein.

This application is related to but does not claim priority to U.S.Provisional patent application Nos.: 61/912,957 filed on Dec. 6, 2013entitled METHOD AND DEVICE FOR SEPARATING HYDROCARBONS AND CONTAMINANTSWITH A SPRAY ASSEMBLY; 62/044,770 filed on Sep. 2, 2014 entitled METHODAND DEVICE FOR SEPARATING HYDROCARBONS AND CONTAMINANTS WITH A SPRAYASSEMBLY; 61/912,959 filed on Dec. 6, 2013 entitled METHOD AND SYSTEM OFMAINTAING A LIQUID LEVEL IN A DISTILLATION TOWER; 61/912,964 filed onDec. 6, 2013 entitled METHOD AND DEVICE FOR SEPARATING A FEED STREAMUSING RADIATION DETECTORS; 61/912,970 filed on Dec. 6, 2013 entitledMETHOD AND SYSTEM OF DEHYDRATING A FEED STREAM PROCESSED IN ADISTILLATION TOWER; 61/912,975 filed on Dec. 6, 2013 entitled METHOD ANDSYSTEM FOR SEPARATING A FEED STREAM WITH A FEED STREAM DISTRIBUTIONMECHANISM; 61/912,978 filed on Dec. 6, 2013 entitled METHOD AND SYSTEMFOR PREVENTING ACCUMULATION OF SOLIDS IN A DISTILLATION TOWER;61/912,984 filed on Dec. 6, 2013 entitled METHOD AND SYSTEM OF MODIFYINGA LIQUID LEVEL DURING START-UP OPERATIONS; 61/912,986 filed on Dec. 6,2013 entitled METHOD AND DEVICE FOR SEPARATING HYDROCARBONS ANDCONTAMINANTS WITH A HEATING MECHANISM TO DESTABILIZE AND/OR PREVENTADHESION OF SOLIDS; 61/912,987 filed on Dec. 6, 2013 entitled METHOD ANDDEVICE FOR SEPARATING HYDROCARBONS AND CONTAMINANTS WITH A SURFACETREATMENT MECHANISM.

BACKGROUND

1. Fields of Disclosure

The disclosure relates generally to the field of fluid separation. Morespecifically, the disclosure relates to the cryogenic separation ofcontaminants, such as acid gas, from a hydrocarbon.

2. Description of Related Art

This section is intended to introduce various aspects of the art, whichmay be associated with the present disclosure. This discussion isintended to provide a framework to facilitate a better understanding ofparticular aspects of the present disclosure. Accordingly, it should beunderstood that this section should be read in this light, and notnecessarily as admissions of prior art.

The production of natural gas hydrocarbons, such as methane and ethane,from a reservoir oftentimes carries with it the incidental production ofnon-hydrocarbon gases. Such gases include contaminants, such as at leastone of carbon dioxide (“CO₂”), hydrogen sulfide (“H₂S”), carbonylsulfide, carbon disulfide and various mercaptans. When a feed streambeing produced from a reservoir includes these contaminants mixed withhydrocarbons, the stream is oftentimes referred to as “sour gas.”

Many natural gas reservoirs have relatively low percentages ofhydrocarbons and relatively high percentages of contaminants.Contaminants may act as a diluent and lower the heat content of thehydrocarbons. Some contaminants, like sulfur-bearing compounds, arenoxious and may even be lethal. Additionally, in the presence of watersome contaminants can become quite corrosive.

It is desirable to remove contaminants from a stream containinghydrocarbons to produce sweet and concentrated hydrocarbons.Specifications for pipeline quality natural gas typically call for amaximum of 2-4% CO₂ and ¼ grain H₂S per 100 scf (4 ppmv) or 5 mg/Nm3H₂S. Specifications for lower temperature processes such as natural gasliquefaction plants or nitrogen rejection units typically require lessthan 50 ppm CO₂.

The separation of contaminants from hydrocarbons is difficult andconsequently significant work has been applied to the development ofhydrocarbon/contaminant separation methods. These methods can be placedinto three general classes: absorption by solvents (physical, chemicaland hybrids), adsorption by solids, and distillation.

Separation by distillation of some mixtures can be relatively simpleand, as such, is widely used in the natural gas industry. However,distillation of mixtures of natural gas hydrocarbons, primarily methane,and one of the most common contaminants in natural gas, carbon dioxide,can present significant difficulties. Conventional distillationprinciples and conventional distillation equipment are predicated on thepresence of only vapor and liquid phases throughout the distillationtower. The separation of CO₂ from methane by distillation involvestemperature and pressure conditions that result in solidification of CO₂if a pipeline or better quality hydrocarbon product is desired. Therequired temperatures are cold temperatures typically referred to ascryogenic temperatures.

Certain cryogenic distillations can overcome the above mentioneddifficulties. These cryogenic distillations provide the appropriatemechanism to handle the formation and subsequent melting of solidsduring the separation of solid-forming contaminants from hydrocarbons.The formation of solid contaminants in equilibrium with vapor-liquidmixtures of hydrocarbons and contaminants at particular conditions oftemperature and pressure takes place in a controlled freeze zonesection.

Sometimes solids can adhere to an internal (e.g., controlled freeze zonewall) of the controlled freeze zone section rather than melt. Adherenceof the solids can result in undesired accumulation of the solids.

The adherence and subsequent accumulation is disadvantageous. Theadherence and subsequent accumulation, if uncontrolled, can interferewith the proper operation of the controlled freeze zone and theeffective separation of methane from the contaminants.

A need exists for improved technology, including technology thatdestabilizes and removes any adhesion of solids to surface(s) in thecontrolled freeze zone section.

SUMMARY

The present disclosure provides a device and method for separatingcontaminants from hydrocarbons, among other things.

A method of separating in a feed stream in a distillation tower maycomprise maintaining a controlled freeze zone section in a distillationtower that operates at a temperature and pressure at which a solidforms; maintaining a melt tray assembly within the controlled freezezone section that operates at a temperature and pressure at which thesolid melts; forming solids in a controlled freeze zone section; raisinga liquid level of a liquid in the melt tray assembly when the solidsaccumulate on a mechanical component in the controlled freeze zonesection; raising a liquid temperature of the liquid while raising theliquid level; and lowering the liquid level after at least one of (a) apredetermined time period has passed and (b) an alternative temperatureof the mechanical component is within an expected temperature range of abaseline temperature of the mechanical component.

A method of producing a hydrocarbon in a distillation tower may comprisemaintaining a controlled freeze zone section in the distillation towerthat operates at a temperature and pressure at which a feed stream formsa solid; maintaining a melt tray assembly within the controlled freezezone section that operates at a temperature and pressure at which thesolid melts; forming solids in the controlled freeze zone section;raising a liquid level of a liquid in the melt tray assembly when thesolids accumulate on a mechanical component in the controlled freezezone section; raising a liquid temperature of the liquid while raisingthe liquid level; lowering the liquid level after at least one of (a) apredetermined time period passed and (b) a detected temperature of themechanical component is within an expected temperature range of abaseline temperature of the mechanical component; and producinghydrocarbons from the feed stream.

The foregoing has broadly outlined the features of the presentdisclosure in order that the detailed description that follows may bebetter understood. Additional features will also be described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects and advantages of the disclosure willbecome apparent from the following description, appending claims and theaccompanying drawings, which are briefly described below.

FIG. 1 is a schematic diagram of a tower with sections within a singlevessel.

FIG. 2 is a schematic diagram of a tower with sections within multiplevessels.

FIG. 3 is a schematic diagram of a tower with sections within a singlevessel.

FIG. 4 is a schematic diagram of a tower with sections within multiplevessels.

FIG. 5 is a schematic diagram of a portion of a middle controlled freezezone section and a lower section of a distillation tower showing some ofthe components of these sections.

FIG. 6 is a flowchart of a method within the scope of the presentdisclosure.

It should be noted that the figures are merely examples and nolimitations on the scope of the present disclosure are intended thereby.Further, the figures are generally not drawn to scale, but are draftedfor purposes of convenience and clarity in illustrating various aspectsof the disclosure.

DETAILED DESCRIPTION

For the purpose of promoting an understanding of the principles of thedisclosure, reference will now be made to the features illustrated inthe drawings and specific language will be used to describe the same. Itwill nevertheless be understood that no limitation of the scope of thedisclosure is thereby intended. Any alterations and furthermodifications, and any further applications of the principles of thedisclosure as described herein are contemplated as would normally occurto one skilled in the art to which the disclosure relates. It will beapparent to those skilled in the relevant art that some features thatare not relevant to the present disclosure may not be shown in thedrawings for the sake of clarity.

As referenced in this application, the terms “stream,” “gas stream,”“vapor stream,” and “liquid stream” refer to different stages of a feedstream as the feed stream is processed in a distillation tower thatseparates methane, the primary hydrocarbon in natural gas, fromcontaminants. Although the phrases “gas stream,” “vapor stream,” and“liquid stream,” refer to situations where a gas, vapor, and liquid ismainly present in the stream, respectively, there may be other phasesalso present within the stream. For example, a gas may also be presentin a “liquid stream.” In some instances, the terms “gas stream” and“vapor stream” may be used interchangeably.

The disclosure relates to a system and method for separating a feedstream in a distillation tower. The system and method helps prevent theaccumulation of solids in the controlled freeze zone section bydisengaging solids that accumulated in the controlled freeze zonesection from the surface(s) where the solids accumulated. The system andmethod disengages solids by increasing the liquid level of warm liquidin a melt tray assembly of a middle controlled freeze zone section ofthe distillation tower. The liquid level can be increased to cover atleast a portion of the solids so as to cause disengagement of the solidsby melting. FIGS. 1-6 of the disclosure display various aspects of thesystem and method.

The system and method may separate a feed stream having methane andcontaminants. The system may comprise a distillation tower 104, 204(FIGS. 1-2). The distillation tower 104, 204 may separate thecontaminants from the methane.

The distillation tower 104, 204 may be separated into three functionalsections: a lower section 106, a middle controlled freeze zone section108 and an upper section 110. The distillation tower 104, 204 mayincorporate three functional sections when the upper section 110 isneeded and/or desired.

The distillation tower 104, 204 may incorporate only two functionalsections when the upper section 110 is not needed and/or desired. Whenthe distillation tower does not include an upper section 110, a portionof vapor leaving the middle controlled freeze zone section 108 may becondensed in a condenser 122 and returned as a liquid stream via a sprayassembly 129. Moreover, lines 18 and 20 may be eliminated, elements 124and 126 may be one and the same, and elements 150 and 128 may be one andthe same. The stream in line 14, now taking the vapors leaving themiddle controlled freeze section 108, directs these vapors to thecondenser 122.

The lower section 106 may also be referred to as a stripper section. Themiddle controlled freeze zone section 108 may also be referred to as acontrolled freeze zone section. The upper section 110 may also bereferred to as a rectifier section.

The sections of the distillation tower 104 may be housed within a singlevessel (FIGS. 1 and 3). For example, the lower section 106, the middlecontrolled freeze zone section 108, and the upper section 110 may behoused within a single vessel 164.

The sections of the distillation tower 204 may be housed within aplurality of vessels to form a split-tower configuration (FIGS. 2 and4). Each of the vessels may be separate from the other vessels. Pipingand/or another suitable mechanism may connect one vessel to anothervessel. In this instance, the lower section 106, middle controlledfreeze zone section 108 and upper section 110 may be housed within twoor more vessels. For example, as shown in FIGS. 2 and 4, the uppersection 110 may be housed within a single vessel 254 and the lower andmiddle controlled freeze zone sections 106, 108 may be housed within asingle vessel 264. When this is the case, a liquid stream exiting theupper section 110, may exit through a liquid outlet bottom 260. Theliquid outlet bottom 260 is at the bottom of the upper section 110.Although not shown, each of the sections may be housed within its ownseparate vessel, or one or more section may be housed within separatevessels, or the upper and middle controlled freeze zone sections may behoused within a single vessel and the lower section may be housed withina single vessel, etc. When sections of the distillation tower are housedwithin vessels, the vessels may be side-by-side along a horizontal lineand/or above each other along a vertical line.

The split-tower configuration may be beneficial in situations where theheight of the distillation tower, motion considerations, and/ortransportation issues, such as for remote locations, need to beconsidered. This split-tower configuration allows for the independentoperation of one or more sections. For example, when the upper sectionis housed within a single vessel and the lower and middle controlledfreeze zone sections are housed within a single vessel, independentgeneration of reflux liquids using a substantially contaminant-free,largely hydrocarbon stream from a packed gas pipeline or an adjacenthydrocarbon line, may occur in the upper section. And the reflux may beused to cool the upper section, establish an appropriate temperatureprofile in the upper section, and/or build up liquid inventory at thebottom of the upper section to serve as an initial source of sprayliquids for the middle controlled freeze zone section. Moreover, themiddle controlled freeze zone and lower sections may be independentlyprepared by chilling the feed stream, feeding it to the optimal locationbe that in the lower section or in the middle controlled freeze zonesection, generating liquids for the lower and the middle controlledfreeze zone sections, and disposing the vapors off the middle controlledfreeze zone section while they are off specification with too high acontaminant content. Also, liquid from the upper section may beintermittently or continuously sprayed, building up liquid level in thebottom of the middle controlled freeze zone section and bringing thecontaminant content in the middle controlled freeze zone section downand near steady state level so that the two vessels may be connected tosend the vapor stream from the middle controlled freeze zone section tothe upper section, continuously spraying liquid from the bottom of theupper section into the middle controlled freeze zone section andstabilizing operations into steady state conditions. The split towerconfiguration may utilize a sump of the upper section as a liquidreceiver for the pump 128, therefore obviating the need for a liquidreceiver 126 in FIGS. 1 and 3.

The system may also include a heat exchanger 100 (FIGS. 1-4). The feedstream 10 may enter the heat exchanger 100 before entering thedistillation tower 104, 204. The feed stream 10 may be cooled within theheat exchanger 100. The heat exchanger 100 helps drop the temperature ofthe feed stream 10 to a level suitable for introduction into thedistillation tower 104, 204.

The system may include an expander device 102 (FIGS. 1-4). The feedstream 10 may enter the expander device 102 before entering thedistillation tower 104, 204. The feed stream 10 may be expanded in theexpander device 102 after exiting the heat exchanger 100. The expanderdevice 102 helps drop the temperature of the feed stream 10 to a levelsuitable for introduction into the distillation tower 104, 204. Theexpander device 102 may be any suitable device, such as a valve. If theexpander device 102 is a valve, the valve may be any suitable valve thatmay aid in cooling the feed stream 10 before it enters the distillationtower 104, 204. For example, the valve 102 may comprise a Joule-Thompson(J-T) valve.

The system may include a feed separator 103 (FIGS. 3-4). The feed streammay enter the feed separator before entering the distillation tower 104,204. The feed separator may separate a feed stream having a mixed liquidand vapor stream into a liquid stream and a vapor stream. Lines 12 mayextend from the feed separator to the distillation tower 104, 204. Oneof the lines 12 may receive the vapor stream from the feed separator.Another one of the lines 12 may receive the liquid stream from the feedseparator. Each of the lines 12 may extend to the same and/or differentsections (i.e. middle controlled freeze zone, and lower sections) of thedistillation tower 104, 204. The expander device 102 may or may not bedownstream of the feed separator 103. The expander device 102 maycomprise a plurality of expander devices 102 such that each line 12 hasan expander device 102.

The system may include a dehydration unit 261 (FIGS. 1-4). The feedstream 10 may enter the dehydration unit 261 before entering thedistillation tower 104, 204. The feed stream 10 enters the dehydrationunit 261 before entering the heat exchanger 100 and/or the expanderdevice 102. The dehydration unit 261 removes water from the feed stream10 to prevent water from later presenting a problem in the heatexchanger 100, expander device 102, feed separator 103, or distillationtower 104, 204. The water can present a problem by forming a separatewater phase (i.e., ice and/or hydrate) that plugs lines, equipment ornegatively affects the distillation process. The dehydration unit 261dehydrates the feed stream to a dew point sufficiently low to ensure aseparate water phase does not form at any point downstream during therest of the process. The dehydration unit may be any suitabledehydration mechanism, such as a molecular sieve or a glycol dehydrationunit.

The system may include a filtering unit (not shown). The feed stream 10may enter the filtering unit before entering the distillation tower 104,204. The filtering unit may remove undesirable contaminants from thefeed stream before the feed stream enters the distillation tower 104,204. Depending on what contaminants are to be removed, the filteringunit may be before or after the dehydration unit 261 and/or before orafter the heat exchanger 100.

The systems may include a line 12 (FIGS. 1-4). The line may also bereferred to as an inlet channel 12. The feed stream 10 may be introducedinto the distillation tower 104, 204 through the line 12. The line 12may extend to the lower section 106 or the middle controlled freeze zonesection 108 of the distillation tower 104, 204. For example, the line 12may extend to the lower section 106 such that the feed stream 10 mayenter the lower section 106 of the distillation tower 104, 204 (FIGS.1-4). The line 12 may directly or indirectly extend to the lower section106 or the middle controlled freeze zone section 108. The line 12 mayextend to an outer surface of the distillation tower 104, 204 beforeentering the distillation tower.

If the system includes the feed separator 103 (FIGS. 3-4), the line 12may comprise a plurality of lines 12. Each line may be the same line asone of the lines that extends from the feed separator to a specificportion of the distillation tower 104, 204.

The lower section 106 is constructed and arranged to separate the feedstream 10 into an enriched contaminant bottom liquid stream (i.e.,liquid stream) and a freezing zone vapor stream (i.e., vapor stream).The lower section 106 separates the feed stream at a temperature andpressure at which no solids form. The liquid stream may comprise agreater quantity of contaminants than of methane. The vapor stream maycomprise a greater quantity of methane than of contaminants. In anycase, the vapor stream is lighter than the liquid stream. As a result,the vapor stream rises from the lower section 106 and the liquid streamfalls to the bottom of the lower section 106.

The lower section 106 may include and/or connect to equipment thatseparates the feed stream. The equipment may comprise any suitableequipment for separating methane from contaminants, such as one or morepacked sections 181, or one or more distillation trays with perforationsdowncomers and weirs (FIGS. 1-4).

The equipment may include components that apply heat to the stream toform the vapor stream and the liquid stream. For example, the equipmentmay comprise a first reboiler 112 that applies heat to the stream. Thefirst reboiler 112 may be located outside of the distillation tower 104,204. The equipment may also comprise a second reboiler 172 that appliesheat to the stream. The second reboiler 172 may be located outside ofthe distillation tower 104, 204. Line 117 may lead from the distillationtower to the second reboiler 172. Line 17 may lead from the secondreboiler 172 to the distillation tower. Additional reboilers, set upsimilarly to the second reboiler described above, may also be used.

The first reboiler 112 may apply heat to the liquid stream that exitsthe lower section 106 through a liquid outlet 160 of the lower section106. The liquid stream may travel from the liquid outlet 160 throughline 28 to reach the first reboiler 112 (FIGS. 1-4). The amount of heatapplied to the liquid stream by the first reboiler 112 can be increasedto separate more methane from contaminants. The more heat applied by thereboiler 112 to the stream, the more methane separated from the liquidcontaminants, though more contaminants will also be vaporized.

The first reboiler 112 may also apply heat to the stream within thedistillation tower 104, 204. Specifically, the heat applied by the firstreboiler 112 warms up the lower section 106. This heat travels up thelower section 106 and supplies heat to warm solids entering a melt trayassembly 139 (FIGS. 1-4) of the middle controlled freeze zone section108 so that the solids form a liquid and/or slurry mix.

The second reboiler 172 applies heat to the stream within the lowersection 106. This heat is applied closer to the middle controlled freezezone section 108 than the heat applied by the first reboiler 112. As aresult, the heat applied by the second reboiler 172 reaches the middlecontrolled freeze zone section 108 faster than the heat applied by thefirst reboiler 112. The second reboiler 172 also helps with energyintegration.

The equipment may include a chimney assembly 135 (FIGS. 1-4). Whilefalling to the bottom of the lower section 106, the liquid stream mayencounter one or more of the chimney assemblies 135.

Each chimney assembly 135 includes a chimney tray 131 that collects theliquid stream within the lower section 106. The liquid stream thatcollects on the chimney tray 131 may be fed to the second reboiler 172.After the liquid stream is heated in the second reboiler 172, the streammay return to the middle controlled freeze zone section 108 to supplyheat to the middle controlled freeze zone section 108 and/or the melttray assembly 139. Unvaporized or partially vaporized stream exiting thesecond reboiler 172 may be fed back to the distillation tower 104, 204below the chimney tray 131. Vapor stream exiting the second reboiler 172may be routed under or above the chimney tray 131 when the vapor streamenters the distillation tower 104, 204.

The chimney tray 131 may include one or more chimneys 137. The chimney137 serves as a channel that the vapor stream in the lower section 106traverses. The vapor stream travels through an opening in the chimneytray 131 at the bottom of the chimney 137 to the top of the chimney 137.The opening is closer to the bottom of the lower section 106 than it isto the bottom of the middle controlled freeze zone section 108. The topis closer to the bottom of the middle controlled freeze zone section 108than it is to the bottom of the lower section 106.

Each chimney 137 has attached to it a chimney cap 133. The chimney cap133 covers a chimney top opening 138 of the chimney 137. The chimney cap133 prevents the liquid stream from entering the chimney 137. The vaporstream exits the chimney assembly 135 via the chimney top opening 138.

After falling to the bottom of the lower section 106, the liquid streamexits the distillation tower 104, 204 through the liquid outlet 160. Theliquid outlet 160 is within the lower section 106 (FIGS. 1-4). Theliquid outlet 160 may be located at the bottom of the lower section 106.

After exiting through the liquid outlet 160, the feed stream may travelvia line 28 to the first reboiler 112. The feed stream may be heated bythe first reboiler 112 and vapor may then re-enter the lower section 106through line 30. Unvaporized liquid may continue out of the distillationprocess via line 24.

The system may include an expander device 114 (FIGS. 1-4). Afterentering line 24, the heated liquid stream may be expanded in theexpander device 114. The expander device 114 may be any suitable device,such as a valve. The valve 114 may be any suitable valve, such as a J-Tvalve.

The system may include a heat exchanger 116 (FIGS. 1-4). The liquidstream heated by the first reboiler 112 may be cooled or heated by theheat exchanger 116. The heat exchanger 116 may be a direct heatexchanger or an indirect heat exchanger. The heat exchanger 116 maycomprise any suitable heat exchanger.

The vapor stream in the lower section 106 rises from the lower section106 to the middle controlled freeze zone section 108. The middlecontrolled freeze zone section 108 is maintained in the distillationtower 104, 204 to operate at a temperature and pressure at which a solidforms, 301 (FIG. 6). The middle controlled freeze zone section 108 isconstructed and arranged to separate the feed stream 10 introduced intothe middle controlled freeze zone section, or into the top of lowersection 106, into a solid and a vapor stream. The solid may be comprisedmore of contaminants than of methane. The vapor stream (i.e.,methane-enriched vapor stream) may comprise more methane thancontaminants.

The middle controlled freeze zone section 108 includes a lower section40 and an upper section 39 (FIG. 5). The lower section 40 is below theupper section 39. The lower section 40 directly abuts the upper section39. The lower section 40 is primarily but not exclusively a heatingsection of the middle controlled freeze zone section 108. The uppersection 39 is primarily but not exclusively a cooling section of themiddle controlled freeze zone section 108. The temperature and pressureof the upper section 39 are chosen so that the solid can form in themiddle controlled freeze zone section 108.

The middle controlled freeze zone section 108 may comprise a melt trayassembly 139 that is maintained in the middle controlled freeze zonesection 108, 302 (FIGS. 1-6). The melt tray assembly 139 is within thelower section 40 of the middle controlled freeze zone section 108. Themelt tray assembly 139 is not within the upper section 39 of the middlecontrolled freeze zone section 108.

The melt tray assembly 139 is constructed and arranged to melt solidsformed in the middle controlled freeze zone section 108. When the warmvapor stream rises from the lower section 106 to the middle controlledfreeze zone section 108, the vapor stream immediately encounters themelt tray assembly 139 and supplies heat to melt the solid. The melttray assembly 139 may comprise at least one of a melt tray 118, a bubblecap 132, a liquid 130 and heat mechanism(s) 134.

The melt tray 118 may collect a liquid and/or slurry mix. The melt tray118 divides at least a portion of the middle controlled freeze zonesection 108 from the lower section 106. The melt tray 118 is at thebottom 45 of the middle controlled freeze zone section 108.

One or more bubble caps 132 may act as a channel for the vapor streamrising from the lower section 106 to the middle controlled freeze zonesection 108. The bubble cap 132 may provide a path for the vapor streamstream up the riser 140 and then down and around the riser 140 to themelt tray 118. The riser 140 is covered by a cap 141. The cap 141prevents the liquid 130 from travelling into the riser and it also helpsprevent solids from travelling into the riser 140. The vapor stream'straversal through the bubble cap 132 allows the vapor stream to transferheat to the liquid 130 within the melt tray assembly 139.

One or more heat mechanisms 134 may further heat up the liquid 130 tofacilitate melting of the solids into a liquid and/or slurry mix. Theheat mechanism(s) 134 may be located anywhere within the melt trayassembly 139. For example, as shown in FIGS. 1-4, a heat mechanism 134may be located around bubble caps 132. The heat mechanism 134 may be anysuitable mechanism, such as a heat coil. The heat source of the heatmechanism 134 may be any suitable heat source.

The liquid 130 in the melt tray assembly is heated by the vapor stream.The liquid 130 may also be heated by the one or more heat mechanisms134. The liquid 130 helps melt the solids formed in the middlecontrolled freeze zone section 108 into a liquid and/or slurry mix.Specifically, the heat transferred by the vapor stream heats up theliquid, thereby enabling the heat to melt the solids. The liquid 130 isat a level sufficient to melt the solids.

The middle controlled freeze zone section 108 may also comprise a sprayassembly 129. The spray assembly 129 cools the vapor stream that risesfrom the lower section 40. The spray assembly 129 sprays a liquid spray,which is cooler than the vapor stream, on the vapor stream to cool thevapor stream. The spray assembly 129 is within the upper section 39. Thespray assembly 129 is not within the lower section 40. The sprayassembly 129 is above the melt tray assembly 139. In other words, themelt tray assembly 139 is below the spray assembly 129.

The spray assembly 129 includes one or more spray nozzles 120 (FIGS.1-4).

Each spray nozzle 120 sprays liquid spray on the vapor stream. The sprayassembly 129 may also include a spray pump 128 (FIGS. 1-4) that pumpsthe liquid spray. Instead of a spray pump 128, gravity may induce flowin the liquid spray.

The liquid spray sprayed by the spray assembly 129 contacts the vaporstream at a temperature and pressure at which solids form. Solids,containing mainly contaminants, form when the liquid spray contacts thevapor stream. The solids fall toward the melt tray assembly 139.

The temperature in the middle controlled freeze zone section 108 coolsdown as the vapor stream travels from the bottom of the middlecontrolled freeze zone section 108 to the top of the middle controlledfreeze zone section 108. The methane in the vapor stream rises from themiddle controlled freeze zone section 108 to the upper section 110. Somecontaminants may remain in the methane and also rise. The contaminantsin the vapor stream tend to condense or solidify with the coldertemperatures and fall to the bottom of the middle controlled freeze zonesection 108.

The solids form the liquid and/or slurry mix when in the liquid 130. Theliquid and/or slurry mix flows from the middle controlled freeze zonesection 108 to the lower distillation section 106. The liquid and/orslurry mix flows from the bottom of the middle controlled freeze zonesection 108 to the top of the lower section 106 via a line 22 (FIGS.1-4). The line 22 may be an exterior line. The line 22 may extend fromthe distillation tower 104, 204. The line 22 may extend from the middlecontrolled freeze zone section 108. The line may extend to the lowersection 106. The line 22 may extend from an outer surface of thedistillation tower 104, 204.

The vapor stream that rises in the middle controlled freeze zone section108 and does not form solids or otherwise fall to the bottom of themiddle controlled freeze zone section 108, rises to the upper section110. The upper section 110 operates at a temperature and pressure andcontaminant concentration at which no solid forms. The upper section 110is constructed and arranged to cool the vapor stream to separate themethane from the contaminants. Reflux in the upper section 110 cools thevapor stream. The reflux is introduced into the upper section 110 vialine 18. Line 18 may extend to the upper section 110. Line 18 may extendfrom an outer surface of the distillation tower 104, 204.

After contacting the reflux in the upper section 110, the feed streamforms a vapor stream and a liquid stream. The vapor stream mainlycomprises methane. The liquid stream comprises relatively morecontaminants. The vapor stream rises in the upper section 110 and theliquid falls to a bottom of the upper section 110.

To facilitate separation of the methane from the contaminants when thestream contacts the reflux, the upper section 110 may include one ormore mass transfer devices 176. Each mass transfer device 176 helpsseparate the methane from the contaminants. Each mass transfer device176 may comprise any suitable separation device, such as a tray withperforations, or a section of random or structured packing to facilitatecontact of the vapor and liquid phases.

After rising, the vapor stream may exit the distillation tower 104, 204through line 14. The line 14 may emanate from an upper part of the uppersection 110. The line 14 may extend from an outer surface of the uppersection 110.

From line 14, the vapor stream may enter a condenser 122. The condenser122 cools the vapor stream to form a cooled stream. The condenser 122 atleast partially condenses the stream.

After exiting the condenser 122, the cooled stream may enter a separator124. The separator 124 separates the vapor stream into liquid and vaporstreams. The separator may be any suitable separator that can separate astream into liquid and vapor streams, such as a reflux drum.

Once separated, the vapor stream may exit the separator 124 as salesproduct. The sales product may travel through line 16 for subsequentsale to a pipeline and/or condensation to be liquefied natural gas.

Once separated, the liquid stream may return to the upper section 110through line 18 as the reflux. The reflux may travel to the uppersection 110 via any suitable mechanism, such as a reflux pump 150 (FIGS.1 and 3) or gravity (FIGS. 2 and 4).

The liquid stream (i.e., freezing zone liquid stream) that falls to thebottom of the upper section 110 collects at the bottom of the uppersection 110. The liquid may collect on tray 183 (FIGS. 1 and 3) or atthe bottommost portion of the upper section 110 (FIGS. 2 and 4). Thecollected liquid may exit the distillation tower 104, 204 through line20 (FIGS. 1 and 3) or outlet 260 (FIGS. 2 and 4). The line 20 mayemanate from the upper section 110. The line 20 may emanate from abottom end of the upper section 110. The line 20 may extend from anouter surface of the upper section 110.

The line 20 and/or outlet 260 connect to a line 41. The line 41 leads tothe spray assembly 129 in the middle controlled freeze zone section 108.The line 41 emanates from the holding vessel 126. The line 41 may extendto an outer surface of the middle controlled freeze zone section 108.

The line 20 and/or outlet 260 may directly or indirectly (FIGS. 1-4)connect to the line 41. When the line 20 and/or outlet 260 directlyconnect to the line 41, the liquid spray may be pumped to the spraynozzle(s) 120 via any suitable mechanism, such as the spray pump 128 orgravity. When the line 20 and/or outlet 260 indirectly connect to theline 41, the lines 20, 41 and/or outlet 260 and line 41 may directlyconnect to a holding vessel 126 (FIGS. 1 and 3). The holding vessel 126may house at least some of the liquid spray before it is sprayed by thenozzle(s). The liquid spray may be pumped from the holding vessel 126 tothe spray nozzle(s) 120 via any suitable mechanism, such as the spraypump 128 (FIGS. 1-2) or gravity. The holding vessel 126 may be neededwhen there is not a sufficient amount of liquid stream at the bottom ofthe upper section 110 to feed the spray nozzles 120.

The system may also include one or more temperature sensors 36 (FIG. 5).Each temperature sensor 36 may be coupled to the same and/or a differentmechanical component. The temperature sensor 36 detects the temperatureof the mechanical component. The mechanical component may be thedistillation tower 104, 204 and/or included in the distillation tower104, 204. For example, to help detect the presence of solids in themiddle controlled freeze zone section 108, the mechanical component maybe the middle controlled freeze zone section 108 or one or moreinternals of the middle controlled freeze zone section 108. For example,to detect whether solids have accumulated on a controlled freeze zonewall 46 of the middle controlled freeze zone section 108, the mechanicalcomponent may be the controlled freeze zone wall 46. If the mechanicalcomponent is the controlled freeze zone wall 46, the mechanicalcomponent may be coupled to an internal surface 31 or to an externalsurface 47 of the controlled freeze zone wall 46 (FIG. 5). The internalsurface 31 is the innermost surface of the controlled freeze zone wall46 and is on an inner surface of the middle controlled freeze zonesection 108. The external surface 47 is the outermost surface of thecontrolled freeze zone wall 46 and is on an outer surface of the middlecontrolled freeze zone section 108.

Before the distillation tower 104, 204 forms any solids, eachtemperature sensor 36 detects a baseline temperature of the mechanicalcomponent. The baseline temperature is within an expected temperaturerange. After the distillation tower 104, 204 forms solids, a temperaturesensor 36 may detect an alternative temperature. The temperature sensor36 may detect the alternative temperature a plurality of times and atdifferent intervals in time. The alternative temperature is compared tothe expected temperature range to see whether the distillation tower104, 204 is operating normally. The expected temperature range is arange of temperatures that indicates that the distillation tower 104,204 is operating normally. Different areas of the distillation tower104, 204 may have their own expected temperature range that is specificto the nature and purpose of a particular section of the distillationtower 104, 204.

The distillation tower 104, 204 is operating not normally when one ormore of a variety of circumstances has occurred. The variety ofcircumstances may include if solids accumulated on a mechanicalcomponent in the middle controlled freeze zone section 108, if themiddle controlled freeze zone section 108 is too warm to form solids, ifthe middle controlled freeze zone section 108 is too cold to melt thesolids in the melt tray assembly 139, etc. For example, if thetemperature sensor 36 is coupled to the controlled freeze zone externalsurface 47 within the upper section 39 of the middle controlled freezezone section 108 then the temperature sensor 36 is expected to detect afairly cold temperature; that is, close to the actual temperature ofliquid spray within the middle controlled freeze zone section 108. If,in this example, the temperature sensor 36 detects a rise in temperaturefrom that expected of the actual temperature of liquid spray, solidshave accumulated on the controlled freeze zone wall 46. In other words,if the detected temperature is outside of the expected temperature rangeby a positive amount, solids have likely accumulated on the controlledfreeze zone wall 46. The solids acts as an insulator so solid adhesionis determined when there is an unexpected rise in temperature read bythe temperature sensor 36 that is a positive amount outside of theexpected temperature range.

If it's determined that the middle controlled freeze zone section 108 isnot operating normally because the expected temperature range indicatessolids have accumulated on a mechanical component of the middlecontrolled freeze zone section 108, a liquid level of the liquid 130 inthe melt tray assembly 139 may be raised, 304 (FIG. 6). Raising theliquid level includes determining whether solids have accumulated on amechanical component. The liquid level may be raised from a normaloperating level. The normal operating level is the level that the liquidneeds to be at to melt solids when the distillation tower 104, 204 isproperly functioning. When the liquid level rises, the liquid level goesfrom a first liquid level 272 to a second liquid level 273 (FIG. 5). Thesecond liquid level is a level where at least a portion of the solidsthat has accumulated is in contact with the liquid 130.

The liquid 130 may be warmer than the solid and, therefore, may cause atleast a portion of the solids in contact with the liquid 130 to detachfrom whatever surface(s) the solids have accumulated on. The liquid mayalso cause the solids to melt. Even if the liquid 130 is not in directcontact with all of the accumulated solids, the contact may besufficient to cause all of the solids to detach by removing enoughpoints or sites of solids adhesion and/or support. If the contact is notsufficient for all of the solids to detach and/or melt, the liquid levelcan be further modified.

The liquid 130 may be warmer than the normal temperature of the liquidto cause the solids to detach and/or melt more quickly when the liquidlevel rises. The liquid 130 may be warmer than the normal temperature ofthe liquid by about 2 to 5 degrees Fahrenheit or 2 to 5 degreesFahrenheit. To make the liquid 130 warmer than the normal temperature,the temperature of the liquid is raised, 305 (FIG. 6). The temperatureof the liquid 130 (i.e., liquid temperature) may be raised by applyingheat using at least one of the heat mechanism 134, the first reboiler112, and the second reboiler 172 utilizing the vapor stream rising fromthe lower section 106 to the middle controlled freeze zone section 108as the means to transfer heat from the reboilers to the melt tray.Another means of effectively warming the melt tray would be to by-passsome portion of the feed gas around one or more stages of inletchilling. This would be particularly applicable to cases where the feedenters the tower just under the melt tray. This would also be a way ofquickly adding heat to the melt tray. The first reboiler and secondreboiler are each examples of an external heating source that isexternal to the melt tray assembly 139. Another example of an externalheating mechanism is external heat tracing. The heat tracing may be onthe external surface 47 of the controlled freeze zone wall 46. The heattracing may be coupled to the external surface 47. The heat tracing maycomprise any suitable electrical heating element that runs along thelength of a pipe or tower.

The liquid level may be raised by at least partially closing a flowcontrolling element 271. The flow controlling element 271 may be locatedon line 22. When the flow controlling element 271 is at least partiallyclosed, the flow controlling element 271 is closed more than it normallyis. During normal operations, the flow controlling element 271 is atleast partially open to enable liquid to travel from the melt trayassembly 139 to the lower section 106 for processing. For example,during normal operations the flow controlling element 271 may be greaterthan 20% open and less than 40% open. During normal operations the flowcontrolling element 271 can be any percentage within the aforementionedpercentages. During normal operations the liquid level may remainsubstantially constant or constant. When the flow controlling element271 is closed more than it normally is, the liquid 130 in the melt trayassembly 139 builds up in the melt tray assembly 139, thereby raising aliquid level from the first liquid level 272 to the second liquid level273. When the flow controlling element 271 is closed more than itnormally is, the flow controlling element may be less than or equal to20% open. The flow controlling element 271 may be any suitable element.For example, the flow controlling element 271 may be a valve.

After being raised, the liquid level may be lowered after at least oneof (i) a predetermined time period has passed and (ii) the alternativetemperature of the mechanical component is within the expectedtemperature range of the baseline temperature of the mechanicalcomponent, 306 (FIG. 6). The predetermined time period is a period oftime that is long enough to allow the liquid in contact with the solidsto detach and/or melt the solids. The predetermined time period may bebetween about 5 to 30 minutes and 5 to 30 minutes.

After at least one of the predetermined time period has passed and thealternative temperature is within an expected temperature range of thebaseline temperature, the liquid level may be lowered from the secondliquid level 273 to the first liquid level 272. In order to lower theliquid level, the flow controlling element 271 may be opened more thanit is when the liquid level is raised. Additionally, the flowcontrolling element 271 may be opened more than during normal operationsso that the liquid level can quickly return to what it is during normaloperations. Once the liquid level is back to what it is during normaloperations, the flow controlling element 271 may be open as much as itis during normal operations. For example, while trying to get back tothe liquid level at normal operations, the flow controlling element maybe greater than or equal to about 40% or greater than or equal to 40%open.

Before lowering the liquid level, the temperature of one or moretemperature sensors 36 can be detected. The detection determines whetheraccumulated adherent solids remains. If accumulated solids remain, thetemperature of the liquid may be further raised to melt the solids. Inaddition or alternatively, the liquid level may be further raised. Oncethe detected temperature helps the determination be made thataccumulated solids do not remain, the liquid level may be lowered.

Steady state CO₂ material balance calculations could be performed aroundthe system to detect the adhesion of solids in the middle controlledfreeze zone section 108. At steady state, the amount of CO₂ flowing intothe system with the feed stream should substantially equal the sum of i)the amount of CO₂ leaving the distillation tower 104, 204 via line 16and ii) the CO₂ leaving the lower section 110 of the distillation tower104, 204 via the liquid outlet 24. If the amount of CO₂ entering thesystem measurably exceeds the CO₂ leaving the system, then CO₂ isaccumulating in the system, possibly as solids in the middle controlledfreeze zone section 108. The amount of CO₂ entering the system may bedetermined by multiplying the feed stream mass flow rate times the CO₂weight percent at the inlet of the distillation tower 104, 204 to obtaina mass CO₂ entering/unit time. The amount of CO₂ exiting thedistillation tower 104, 204 via line 16 and/or liquid outlet 160 may bedetermined by multiplying the relevant exiting gas (or liquid) mass flowrates times their respective CO₂ weight percent, and summing them toobtain a mass CO₂ exiting/unit time. The difference of CO₂ enteringminus CO₂ exiting represents the instantaneous rate of CO₂ massaccumulation (or loss) in the system at that point in time. Bycollecting a series of these differences and multiplying them byappropriate time increments, it is possible to sum those productstogether to determine if there is a net gain (or loss) of CO₂ in thesystem over that period. These measurements may be be facilitated by theuse of Coriolis flow meters, which measure mass flow rates directly andaccurately.

Because what would otherwise appear to indicate an accumulation of CO₂in the middle controlled freeze zone section 108 may be due toincreasing liquid levels in the middle controlled freeze zone section108, corrections may be made for changing levels of fluid that containCO₂ (e.g., melt tray assembly liquid level, reboiler liquid level).Appropriate factors may be considered to convert these liquid levelchanges to mass changes. The mass changes may then be multiplied bytheir respective CO₂ weight percent. If the total apparent CO₂accumulation as calculated by material balance exceeds the CO₂accumulation as measured by changing liquid levels, then solids may bebuilding in the middle controlled freeze zone section 108 of thedistillation tower 104, 204.

Persons skilled in the technical field will readily recognize that inpractical applications of the disclosed methodology, one or more stepsmay be performed on a computer, typically a suitably programmed digitalcomputer. Further, some portions of the detailed descriptions whichfollow are presented in terms of procedures, steps, logic blocks,processing and other symbolic representations of operations on data bitswithin a computer memory. These descriptions and representations are themeans used by those skilled in the data processing arts to mosteffectively convey the substance of their work to others skilled in theart. In the present application, a procedure, step, logic block,process, or the like, is conceived to be a self-consistent sequence ofsteps or instructions leading to a desired result. The steps are thoserequiring physical manipulations of physical quantities. Usually,although not necessarily, these quantities take the form of electricalor magnetic signals capable of being stored, transferred, combined,compared, and otherwise manipulated in a computer system.

It should be borne in mind, however, that all of these and similar termsare to be associated with the appropriate physical quantities and aremerely convenient labels applied to these quantities. Unlessspecifically stated otherwise as apparent from the followingdiscussions, it is appreciated that throughout the present application,discussions utilizing the terms such as “processing,” “computing,”“calculating,” “detecting,” “determining,” “displaying,” “copying,”“producing,” “storing,” “accumulating,” “adding,” “applying,”“identifting,” “consolidating,” “waiting,” “including,” “executing,”“maintaining,” “updating,” “creating,” “implementing,” “generating,”“transforming,” or the like, may refer to the action and processes of acomputer system, or similar electronic computing device, thatmanipulates and transforms data represented as physical (electronic)quantities within the computer system's registers and memories intoother data similarly represented as physical quantities within thecomputer system memories or registers or other such information storage,transmission or display devices.

It is important to note that the steps depicted in FIG. 6 are providedfor illustrative purposes only and a particular step may not be requiredto perform the inventive methodology. The claims, and only the claims,define the inventive system and methodology.

Aspects of the present disclosure may also relate to an apparatus forperforming the operations herein. This apparatus may be speciallyconstructed for the required purposes, or it may comprise ageneral-purpose computer selectively activated or reconfigured by acomputer program stored in the computer. Such a computer program may bestored in a computer readable medium. A computer-readable mediumincludes any mechanism for storing or transmitting information in a formreadable by a machine (e.g., a computer). For example, but not limitedto, a computer-readable (e.g., machine-readable) medium includes amachine (e.g., a computer) readable storage medium (e.g., read onlymemory (“ROM”), random access memory (“RAM”), magnetic disk storagemedia, optical storage media, flash memory devices, etc.), and a machine(e.g., computer) readable transmission medium (electrical, optical,acoustical or other form of propagated signals (e.g., carrier waves,infrared signals, digital signals, etc.). The computer-readable mediummay be non-transitory. The amounts determined may be displayed in theoperator's console.

Furthermore, as will be apparent to one of ordinary skill in therelevant art, the modules, features, attributes, methodologies, andother aspects of the disclosure can be implemented as software,hardware, firmware or any combination of the three. Of course, wherevera component of the present disclosure is implemented as software, thecomponent can be implemented as a standalone program, as part of alarger program, as a plurality of separate programs, as a statically ordynamically linked library, as a kernel loadable module, as a devicedriver, and/or in every and any other way known now or in the future tothose of skill in the art of computer programming. Additionally, thepresent disclosure is in no way limited to implementation in anyspecific operating system or environment.

Disclosed aspects may be used in hydrocarbon management activities. Asused herein, “hydrocarbon management” or “managing hydrocarbons”includes hydrocarbon extraction, hydrocarbon production, hydrocarbonexploration, identifying potential hydrocarbon resources, identifyingwell locations, determining well injection and/or extraction rates,identifying reservoir connectivity, acquiring, disposing of and/orabandoning hydrocarbon resources, reviewing prior hydrocarbon managementdecisions, and any other hydrocarbon-related acts or activities. Theterm “hydrocarbon management” is also used for the injection or storageof hydrocarbons or CO₂, for example the sequestration of CO₂, such asreservoir evaluation, development planning, and reservoir management.The disclosed methodologies and techniques may be used to producehydrocarbons in a feed stream extracted from, for example, a subsurfaceregion. The feed stream extracted may be processed in the distillationtower 104, 204 and separated into hydrocarbons and contaminants. Theseparated hydrocarbons exit the middle controlled freeze zone section108 or the upper section 110 of the distillation tower. Some or all ofthe hydrocarbons that exit are produced, 307. Hydrocarbon extraction maybe conducted to remove the feed stream from for example, the subsurfaceregion, which may be accomplished by drilling an oil well using oil welldrilling equipment. The equipment and techniques used to drill a welland/or extract the hydrocarbons are well known by those skilled in therelevant art. Other hydrocarbon extraction activities and, moregenerally, other hydrocarbon management activities, may be performedaccording to known principles.

As utilized herein, the terms “approximately,” “about,” “substantially,”and similar terms are intended to have a broad meaning in harmony withthe common and accepted usage by those of ordinary skill in the art towhich the subject matter of this disclosure pertains. It should beunderstood by those of skill in the art who review this disclosure thatthese terms are intended to allow a description of certain featuresdescribed and claimed without restricting the scope of these features tothe precise numeral ranges provided. Accordingly, these terms should beinterpreted as indicating that insubstantial or inconsequentialmodifications or alterations of the subject matter described areconsidered to be within the scope of the disclosure.

For the purpose of this disclosure, the term “coupled” means the joiningof two members directly or indirectly to one another. Such joining maybe stationary or moveable in nature. Such joining may be achieved withthe two members or the two members and any additional intermediatemembers being integrally formed as a single unitary body with oneanother or with the two members or the two members and any additionalintermediate members being attached to one another. Such joining may bepermanent in nature or may be removable or releasable in nature.

It should be understood that numerous changes, modifications, andalternatives to the preceding disclosure can be made without departingfrom the scope of the disclosure. The preceding description, therefore,is not meant to limit the scope of the disclosure. Rather, the scope ofthe disclosure is to be determined only by the appended claims and theirequivalents. It is also contemplated that structures and features in thepresent examples can be altered, rearranged, substituted, deleted,duplicated, combined, or added to each other.

The articles “the”, “a” and “an” are not necessarily limited to meanonly one, but rather are inclusive and open ended so as to include,optionally, multiple such elements.

What is claimed is:
 1. A method of separating a feed stream in adistillation tower comprising: maintaining a controlled freeze zonesection in a distillation tower that operates at a temperature andpressure at which a solid forms; maintaining a melt tray assembly withinthe controlled freeze zone section that operates at a temperature andpressure at which the solid melts; forming solids in the controlledfreeze zone section; raising a liquid level of a liquid in the melt trayassembly when the solids accumulate on a mechanical component in thecontrolled freeze zone section; raising a liquid temperature of theliquid while raising the liquid level; and lowering the liquid levelafter at least one of (a) a predetermined time period has passed and (b)an alternative temperature of the mechanical component is within anexpected temperature range of a baseline temperature of the mechanicalcomponent.
 2. The method of claim 1, wherein raising the liquid levelcomprises determining whether the solids have accumulated on themechanical component.
 3. The method of claim 1, wherein the mechanicalcomponent comprises a controlled freeze zone wall.
 4. The method ofclaim 1, wherein the predetermined time period is about 5 to 30 minutes.5. The method of claim 1, wherein increasing the liquid temperaturecomprises applying heat to the liquid with at least one of (i) a heatmechanism included in the melt tray assembly and (ii) an externalheating mechanism that is external to the melt tray assembly.
 6. Themethod of claim 5, wherein the heat mechanism comprises a melt coil. 7.The method of claim 5, wherein the external heating mechanism comprisesat least one of a first reboiler, a second reboiler and a vapor stream.8. The method of claim 1, further comprising detecting the baselinetemperature before forming the solids in the controlled freeze zonesection; and detecting the alternative temperature after forming thesolids.
 9. The method of claim 8, further comprising repeatedlydetecting the alternative temperature and repeatedly determining whetherthe alternative temperature is within the expected temperature range.10. A method of producing a hydrocarbon in a distillation towercomprising: maintaining a controlled freeze zone section in thedistillation tower that operates at a temperature and pressure at whicha feed stream forms a solid; maintaining a melt tray assembly within thecontrolled freeze zone section that operates at a temperature andpressure at which the solid melts; forming solids in the controlledfreeze zone section; raising a liquid level of a liquid in the melt trayassembly when the solids accumulate on a mechanical component in thecontrolled freeze zone section; raising a liquid temperature of theliquid while raising the liquid level; lowering the liquid level afterat least one of (a) a predetermined time period passed and (b) adetected temperature of the mechanical component is within an expectedtemperature range of a baseline temperature of the mechanical component;and producing hydrocarbons from the feed stream.
 11. The method of claim10, wherein raising the liquid level comprises determining whether thesolids have accumulated on the mechanical component.
 12. The method ofclaim 10, wherein the mechanical component comprises a controlled freezezone wall.
 13. The method of claim 10, wherein the predetermined timeperiod is about 5 to 30 minutes.
 14. The method of claim 10, whereinincreasing the liquid temperature comprises applying heat to the liquidwith at least one of (i) a heat mechanism included in the melt trayassembly and (ii) an external heating mechanism that is external to themelt tray assembly.
 15. The method of claim 14, wherein the heatmechanism comprises a melt coil.
 16. The method of claim 14, wherein theexternal heating mechanism comprises at least one of a first reboiler, asecond reboiler,a vapor stream, and a heat tracing.
 17. The method ofclaim 10, further comprising detecting the baseline temperature beforeforming the solid in the controlled freeze zone section; and detectingthe alternative temperature after forming the solids.
 18. The method ofclaim 17, further comprising repeatedly detecting the alternativetemperature and repeatedly determining whether the alternativetemperature is within the expected temperature range.